Most golf balls comprise a center or core surrounded by one or two layers, either a cover or a mantle and a cover. The core may be formed of a liquid or of a solid polymeric material such as polybutadiene elastomers mixed with acrylate or methacylate metal salts and the mantle and cover layers are formed of an ionomer resin. The present invention relates to an improved isothermal molding platen for manufacturing and curing solid golf ball cores.
It is known in the art to manufacture solid golf ball cores or centers using a heated mold assembly. Plugs of core material are arranged in recesses of one of a pair of mold plates. The plates are brought together to define spherical cavities within which a plug is arranged. Heated platens at the rear of the mold plates heat the molds to cure the plugs under pressure, thereby to form solid spherical cores.
While the prior mold assemblies operate satisfactorily, the heated platens suffer from uneven heat distribution, particularly at the perimeter thereof. Thus golf ball cores formed at the edges of the mold plates take longer to cure than those toward the center. This results in uneven curing of the centers within the mold plates or an increase in the mold cycle times to allow for adequate curing of all of the cores.
The present invention was developed in order to overcome these and other drawbacks of the prior golf ball core mold devices by providing an improved heating platen with uniform temperature distribution across its surface.
Accordingly, it is a primary object of the present invention to provide a device for heating a mold used to manufacture and cure golf ball centers including a platen having planar top and bottom surfaces and a generally rectangular vertical cross-sectional configuration, the platen containing at least one first channel and at least one second channel therein. A heater, which may comprise steam or an electric element, is arranged within the first channel for heating the top and bottom platen surfaces. Isobars are arranged in the second channel for balancing the distribution of heat across the top and bottom surfaces. Accordingly, temperature gradients within the platen surfaces are eliminated.
According to a more specific embodiment of the invention, the heating platen is connected with upper and lower support plates each containing a plurality of hemispherical cavities in opposed surfaces thereof, the upper and lower hemispherical cavities being adapted to mate to define a plurality of spherical cavities when the plates are brought together. Plugs of core material arranged in the spherical cavities are cured by the heat from the isothermal platens. Because of the even temperature distribution of the platens, the plugs are all cured at the same rate.
According to a further embodiment of the invention, the isobars include an outer sheath and an inner metallic wick defining an evacuated chamber. The isobars are charged with a working fluid, such as water, which changes phase with the application of heat.